1. Pediatrics. 2017 Nov;140(5). pii: e20170508. doi: 10.1542/peds.2017-0508.

Drinking Water to Prevent Postvaccination Presyncope in Adolescents: A Randomized
Trial.

Kemper AR(1), Barnett ED(2), Walter EB(3), Hornik C(3), Pierre-Joseph N(2),
Broder KR(4), Silverstein M(2), Harrington T(4).

Author information: 
(1)Division of Ambulatory Pediatrics, Nationwide Children's Hospital, Columbus,
Ohio; alex.kemper@nationwidechildrens.org.
(2)Department of Pediatrics, School of Medicine, Boston University, Boston,
Massachusetts.
(3)Department of Pediatrics, Duke University, Durham, North Carolina; and.
(4)Division of Healthcare Quality Promotion, Immunization Safety Office, Centers 
for Disease Control and Prevention, Atlanta, Georgia.

BACKGROUND AND OBJECTIVES: Postvaccination syncope can cause injury. Drinking
water prephlebotomy increases peripheral vascular tone, decreasing risk of
blood-donation presyncope and syncope. This study evaluated whether drinking
water prevaccination reduces postvaccination presyncope, a potential syncope
precursor.
METHODS: We conducted a randomized trial of subjects aged 11 to 21 years
receiving ≥1 intramuscular vaccine in primary care clinics. Intervention subjects
were encouraged to drink 500 mL of water, with vaccination recommended 10 to 60
minutes later. Control subjects received usual care. Presyncope symptoms were
assessed with a 12-item survey during the 20-minutes postvaccination. Symptoms
were classified with a primary cutoff sensitive for presyncope, and a secondary, 
more restrictive cutoff requiring greater symptoms. Results were adjusted for
clustering by recruitment center.
RESULTS: There were 906 subjects randomly assigned to the control group and 901
subjects randomly assigned to the intervention group. None had syncope.
Presyncope occurred in 36.2% of subjects by using the primary definition, and in 
8.0% of subjects by using the restrictive definition. There were no significant
differences in presyncope by intervention group for the primary (1-sided test, P 
= .24) or restrictive outcome (1-sided test, P = .17). Among intervention
subjects vaccinated within 10 to 60 minutes after drinking all 500 mL of water (n
= 519), no reduction in presyncope was observed for the primary or restrictive
outcome (1-sided tests, P = .13, P = .17). In multivariable regression analysis, 
presyncope was associated with younger age, history of passing out or nearly
passing out after a shot or blood draw, prevaccination anxiety, receiving >1
injected vaccine, and greater postvaccination pain.
CONCLUSIONS: Drinking water before vaccination did not prevent postvaccination
presyncope. Predictors of postvaccination presyncope suggest opportunities for
presyncope and syncope prevention interventions.

Copyright © 2017 by the American Academy of Pediatrics.

DOI: 10.1542/peds.2017-0508 
PMCID: PMC6075677
PMID: 29061871  [Indexed for MEDLINE]

Conflict of interest statement: POTENTIAL CONFLICT OF INTEREST: The authors have 
indicated they have no potential conflicts of interest to disclose.